How to Generate UUIDs in JavaScript: Modern Browser API and Node.js

The Modern Native API: `crypto.randomUUID()`

For years, generating a UUID in JavaScript required installing the external `uuid` npm package. Today, the **Web Cryptography API** provides native UUID generation across all modern JavaScript runtimes.

// Native in modern browsers, Node.js 16.7+, Bun, and Deno:
const id = crypto.randomUUID();
console.log(id); 
// Outputs: "c9a646d3-9c61-4cd7-893e-8cba475a6350"

Browser & Runtime Support - **Chrome / Edge:** Version 92+ - **Safari:** Version 15.4+ - **Firefox:** Version 95+ - **Node.js:** Version 14.17.0+ (global `crypto` available in 19.0+)

Important Security Context: HTTPS Required In browser environments, `window.crypto.randomUUID()` is only accessible in **secure contexts** (pages served over `https://` or `localhost`). Calling it on an insecure plain HTTP origin results in: ```text TypeError: crypto.randomUUID is not a function ```

Safe Cross-Platform Fallback If your code needs to support older legacy environments or non-secure HTTP contexts:

function safeRandomUUID() {
  if (typeof crypto !== 'undefined' && typeof crypto.randomUUID === 'function') {
    return crypto.randomUUID();
  }
  if (typeof crypto !== 'undefined' && typeof crypto.getRandomValues === 'function') {
    const bytes = new Uint8Array(16);
    crypto.getRandomValues(bytes);
    bytes[6] = (bytes[6] & 0x0f) | 0x40; // Version 4
    bytes[8] = (bytes[8] & 0x3f) | 0x80; // Variant 10
    return Array.from(bytes, (b, i) => 
      ([4, 6, 8, 10].includes(i) ? '-' : '') + b.toString(16).padStart(2, '0')
    ).join('');
  }
  throw new Error("No cryptographically secure random source available.");
}

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